This invention relates to a container for the transport and storage of metallic mercury (Hg). It relates particularly to a container for the transport and storage of refined, high purity mercury and to prevent the contamination and leakage of the mercury.
Metallic mercury is used for many purposes such as lamps, electrical equipment, thermometers, barometers and many other industrial and consumer products. Many of these products require mercury of very high purity.
Previously, mercury was shipped from the producer or refiner to a user in a glass bottle or flask sealed with a screw cap or other stopper. These containers are not completely filled but are provided with a headspace sufficient to permit the expansion of the mercury due to a rise in temperature during its transport or storage. The air remaining in the headspace of the bottle or flask will, in time, react with the mercury and form mercuric oxide products so that high purity mercury is sometimes rendered unsuitable for uses that require mercury of very high purity. The contaminated mercury must then be further refined or filtered to remove the oxidation impurities. The mercuric oxides also form a permanent ring on the interior surface of the container that prevents the reuse or recycling of the container. The toxicity of the residual mercury in such containers requires special and expensive disposal of the used containers. Attempts to fill the headspace with a nonoxidizing atmosphere have not been successful since they require an airtight cap or stopper and the container once opened, loses the special atmosphere.
In addition, special care must be used in filling the bottles so that there remains sufficient headspace to permit considerable expansion of the mercury. If the headspace becomes completely filled with the expanded mercury, the mercury will leak out around the threads of the cap because of capillary attraction and rise. Since mercury is toxic, such leakage could present a serious health hazard.